Justification:
The species is widespread and abundant, with current range-wide population estimates in the hundreds of thousands. Although bycatch in high-seas drift gillnet fisheries during the 1970s and 1980s may have caused population declines, these fisheries have been banned since 1993. Current takes and threats are small relative to reported global population size.

Pacific White-sided Dolphins inhabit temperate waters of the North Pacific and some adjacent seas (Sea of Japan, southern Okhotsk Sea, the southern Bering Sea and southern Gulf of California) (Brownell et al. 1999, Van Waerebeek and Würsig 2002). Their range includes continental slope waters of the Western North Pacific as far south as southern China, shelf and slope waters of the eastern North Pacific from the Gulf of Alaska southward to Baja California, Mexico, and deep offshore waters of the North Pacific between about 35˚N and 47˚N latitude (Hobbs and Jones 1993).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.

Two separate estimates of abundance have been made for waters of the central North Pacific, suggesting that 900,000–1,000,000 Pacific White-sided Dolphins may inhabit this oceanic region (Buckland et al. 1993, Miyashita 1993); however, precision was low for both studies, and vessel attraction probably resulted in a substantial overestimation of population size (Buckland et al. 1993). In the eastern North Pacific, the distribution of this species has been documented to vary dramatically with oceanographic conditions (Heise 1997, Forney and Barlow 1998), and abundance estimates along the U.S. West Coast have ranged from about 13,000 to 122,000 (Forney et al 1995, Barlow and Forney, in press). The average abundance in this region during 1996–2001 was estimated to be about 24,000 (Barlow and Forney, in press).

Separate subpopulations have been identified in the southern portions of the species range, off the west coast of North America (Lux et al. 1997) and in Japan (Hayano et al. 2004).

Pacific White-sided Dolphins inhabit temperate oceanic waters across the North Pacific, as well as shelf and slope waters of the North Pacific continental margins (see distribution plots in Carretta et al. 2006), and in some inland waterways (e.g. British Columbia; Heise 1997).

Historically, the greatest threats to Pacific White-sided Dolphins were the high-seas drift gillnet fisheries for salmon and squid, which operated throughout the central and western North Pacific between about 35˚N and 47˚N (Hobbs and Jones 1993). Effort in these fisheries increased during the 1970s and peaked during the 1980s before an United Nations moratorium went into effect in January 1993. Bycatch estimates are only available for a subset of the total fishing effort. The Japanese squid driftnet fishery killed an estimated 6,100 animals during 1989, and all fisheries combined killed an estimated 5,759 during 1990 (Hobbs and Jones 1993). During the 1970s and 1980s, the combined high-seas driftnet fisheries likely killed on the order of 100,000 Pacific White-sided Dolphins. Although there is great uncertainty in the total population size, these bycatch levels may have caused some, but not substantial, population depletion (Hobbs and Jones 1993).

Smaller catches (e.g., at least 194 in 1987) are reported from the Japanese land-based salmon drift net fishery, and small numbers are taken yearly in seines, set nets, and trap nets around Japan (Brownell et al. 1999). Pacific White-sided Dolphins have never been primary targets of Japanese drive fisheries, but they were harpooned in Japanese waters during the 1940s, and cull programs killed at least 466 Pacific White-sided Dolphins in Japanese waters between 1976 and 1980. The Japanese government is currently (2007) considering a renewed direct harvest of this species (Kasuya pers. comm.). The potential for renewed directed takes in Japanese waters, coupled with evidence for population substructure, particularly at the southern ends of this species' range, may require the re-examination of the threat to this species.

In the eastern Pacific, a total of 424 Pacific White-sided Dolphins were estimated killed in the U.S. West Coast shark and swordfish driftnet fishery between 1988 and 2002 (Perkins et al. 1994; Julian and Beeson 1998, Carretta et al. 2005). Additional low levels of mortality have been documented for bottom-set gillnets in California coastal waters, for drift gill nets in British Columbia and Alaska, and for trawl fisheries in Alaska; however, no overall mortality estimates are available for these fisheries. Pacific White-sided Dolphins are rarely taken in the tuna purse seine fishery in the eastern tropical Pacific, because most of the fishing takes place south of the range of these dolphins (Brownell et al. 1999). None of these sources of eastern North Pacific mortality appears of a sufficient magnitude to have caused a population decline in this region.

The most significant international conservation measure for this species was the United Nations (U.N.) moratorium on high-seas driftnet fishing implemented in 1993. In the eastern North Pacific, the U.S drift gillnet fishery has been required since 1996 to use acoustic warning devices (pingers) to reduce cetacean bycatch; however, low levels of bycatch of Lagenorhynchus obliquidens have continued (Carretta et al. 2005).